Results from deuterium-tritium tokamak confinement experiments

Hawryluk, R. J.

doi:10.1103/revmodphys.70.537

Cited by 122 publications

(92 citation statements)

References 259 publications

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“…As observed in practically all tokamaks, the energy and particle confinement improves with increasing atomic weight of the isotope used, from hydrogen to deuterium to tritium (see, e.g., Refs. [1][2][3]). This fact is of crucial importance for the performance of future thermonuclear reactors, which will operate with a mixture of deuterium and tritium rather than present devices which normally use either hydrogen or deuterium.…”

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“…Plasma states, where improved confinement is accompanied by peaked density profiles, reveal a significantly stronger mass dependence. For example, in supershots in Tokamak Fusion Test Reactor (TFTR) E scales as A 0:85 i [2], in pellet fueled plasmas in ASDEX [1], in the radiation improved (RI) mode in TEXTOR [5] and in discharges with improved Ohmic confinement [1],…”

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Nature of the Isotope Effect on Transport in Tokamaks

2004

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The reduction of energy and particle losses with the increasing mass of the hydrogen isotope is more pronounced under conditions of improved confinement when the dominant ion temperature gradient instability is suppressed and other channels of anomalous transport are of importance. In this Letter, we reconsider the dissipative trapped electron (DTE) instability by taking into account finite Larmor radius effects in the analysis of the ion response to perturbations. By applying the improved mixing length approximation in order to estimate the transport coefficients, it is demonstrated that DTE contribution is intrinsically dependent on the isotope mass and provides a plausible explanation for the isotope effect. Contrary to the common belief, it is shown that the DTE turbulence may be of importance for reactor plasmas of low collisionality. As observed in practically all tokamaks, the energy and particle confinement improves with increasing atomic weight of the isotope used, from hydrogen to deuterium to tritium (see, e.g., Refs. [1][2][3]). This fact is of crucial importance for the performance of future thermonuclear reactors, which will operate with a mixture of deuterium and tritium rather than present devices which normally use either hydrogen or deuterium. However, in spite of its fundamental significance, the isotope effect is still one of the least understood phenomena in the physics of tokamak transport.Analysis of the experimental database shows that the isotope effect on confinement depends essentially on the mode of tokamak operation. Thus, the most recent scalings for the energy confinement time E [4] A pattern in this puzzling picture can be found by noting that the strongest improvement with A i takes place if the ion temperature gradient (ITG) instability, which is commonly considered as the main source of anomalous transport [6], is suppressed. This is the case both for the edge barrier in the H mode and for other regimes of improved confinement where ITG is subdued by the density gradient in a large part of the plasma volume (see, e.g., analysis of the L-RI transition in Refs. [7,8]). On the contrary, under conditions where the transport is dominated by ITG modes the confinement deteriorates with increasing A i . For the case of the plasma core in the H mode, this fact was explained in Ref. [9] by applying the mixing length approximation (MLA) [6,10,11], in which max =k 2 max is used as an estimate for transport coefficients. Here max is the maximum value of the instability growth rate considered as a function of the perpendicular wave number k and k max is the k-value where max is reached. For the ITG instability both max and k max vary as A ÿ0:5 i [6,12] and the characteristic heat diffusivity A 0:5 i . Since E 1= , the scaling above is in qualitative agreement with the decrease of the core confinement in the H mode with increasing isotope atomic weight. The same result follows from the so-called improved mixing length approximation (IMLA) [6,13], which takes into account the phase shift betw...

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Nature of the Isotope Effect on Transport in Tokamaks

2004

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“…The classical counterpart of the expansion time in momentum τ p exp is the momentum transfer time, or the deflection time τ d . Thus, if τ p exp τ d , the expansion in momentum could make collision frequency and cross-section much larger than that with classical theories [7][8][9]. By linear extrapolation, however, the expansion time in momentum would be of the order of 10 4 sec for v 0 ∼ 10 6 m/s, and is of little interest for fast particles.…”

Section: Quantum Mechanical ∇B Motionmentioning

confidence: 99%

Numerical Analysis of Quantum Mechanical ∇B Drift

Oikawa

Shimazaki

Okubo

2011

Plasma and Fusion Research

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We have solved the two-dimensional time-dependent Schrödinger equation for a single particle in the presence of a nonuniform magnetic field for initial speeds of 10-100 m/s. By linear extrapolation, it is shown that the variance, or the uncertainty, in position would reach the square of the interparticle separation n −2/3 with a number density of n = 10 20 m −3 in a time interval of the order of 10 −4 sec. After this time the wavefunctions of neighboring particles would overlap, as a result the conventional classical analysis may lose its validity: Plasmas may behave more-or-less like extremely-low-density liquids, not gases, since the size of each particle is of the same order of the interparticle separation.

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“…Moreover, TFTR safely handled 1 M curies of tritium, with rigorous accounting. A review of the D-T results from TFTR has been published by Hawryluk [5].…”

Section: Grand Challenge Of Burning Plasmasmentioning

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Progress Towards Burning Plasmas

Dam

2009

Plasma and Fusion Research

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The next frontier for fusion science is the study of burning plasmas. The international ITER facility will advance research efforts into this new regime. In this paper we will first define burning plasmas and describe their distinctive features. One such feature is dominant self-heating (exothermic) by a large population of alpha particles, created from thermonuclear reactions. Next, we will briefly review how previous experiments on JET and TFTR to attain breakeven have laid the foundation for taking the present step to ITER. Then, we will describe various physics and technology issues that need to be addressed for burning plasmas. In addition to the scientific opportunities, we will also describe how ITER, being operated as a large-scale international project, is making progress in terms of organization, mission, funding, and programmatic coordination worldwide.

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Results from deuterium-tritium tokamak confinement experiments

Cited by 122 publications

References 259 publications

Nature of the Isotope Effect on Transport in Tokamaks

Nature of the Isotope Effect on Transport in Tokamaks

Numerical Analysis of Quantum Mechanical ∇B Drift

Progress Towards Burning Plasmas

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